Surgical systems including a power loss mitigation subsystem

ABSTRACT

Systems, circuits, and methods to mitigate effects of short-term power losses in medical systems are provided. An exemplary surgical system includes a fluidics subsystem, a surgical instrument subsystem that couples to a surgical instrument and a power supply subsystem coupled to the surgical instrument subsystem. The power supply subsystem includes a main power supply connectable to AC mains to generate a voltage, a power bus connected to the main power supply, an alternate power supply, and a circuit that monitors the voltage on the power bus for powering the surgical instrument subsystem. The circuit automatically connects the power bus to the alternate power supply when the voltage drops below a reference voltage due to a power loss from the main power supply.

This application is a continuation of U.S. Non-Provisional patentapplication Ser. No. 15/096,452 titled “SURGICAL SYSTEMS INCLUDING APOWER LOSS MITIGATION SUBSYSTEM,” filed on Apr. 12, 2016, whose inventoris Fred Mercado, which is hereby incorporated by reference in itsentirety as though fully and completely set forth herein.

TECHNICAL FIELD

The present disclosure is directed to methods and systems formaintaining a continuous power supply for a medical system or deviceduring a power interruption.

BACKGROUND

Increasingly, medical procedures are performed in connection with theuse of sophisticated medical systems, such as diagnostic systems,monitoring systems, and surgical systems. The sophisticated medicalsystems may rely on complex electronics and complex circuits to performtheir diagnostic, monitoring, and surgical tasks. The degree ofimportance of maintaining a continuous power supply to such medicalsystems can vary according to the tasks associated with such systems.

For example, when a surgeon is performing a surgical procedure using asurgical system or instrument and the system or instrument experienceseven a short-term power loss, the short-term power loss may alter theperformance of the system or instrument in such a way that adverselyaffect the efficacy and results of the procedure. The complexity of themachine and the nature of the procedure may increase the risksassociated with such short-term power losses. While efforts are taken tomaintain continuous power in the power grid, there is still a need toprovide for a power loss mitigation system at the level of the medicalsystems themselves.

SUMMARY

The present disclosure is directed to systems, circuits, and methods formitigating temporary power losses.

Exemplary medical systems are provided herein. An exemplary ophthalmicsurgical system may include a fluidics subsystem, a surgical instrumentsubsystem that couples to a surgical instrument, and a power supplysubsystem coupled to the surgical instrument subsystem. The fluidicssubsystem may be coupled to the surgical instrument subsystem. The powersupply subsystem may include a main power supply connectable to AC mainsto generate a voltage, a power bus connected to the main power supply,an alternate power supply, and a circuit that monitors the voltage onthe power bus for powering the surgical instrument subsystem. Thecircuit may automatically connect the power bus to the alternate powersupply when the voltage drops below a reference voltage due to a powerloss from the main power supply.

Other exemplary systems are provided herein. An exemplary surgicalsystem may include a surgical instrument subsystem and a power supplysubsystem coupled to the surgical instrument subsystem. The surgicalinstrument subsystem may be connected to a surgical instrument. Thepower supply subsystem may include a main power supply connectable to ACmains to generate a voltage, a power bus connected to the main powersupply, an alternate power supply, and a circuit that monitors thevoltage on the power bus. The circuit may automatically connect thepower bus to the alternate power supply when the voltage drops below areference voltage due to a power loss from the main power supply.

Exemplary methods of mitigating a short-term power loss in a surgicalsystem are provided. An exemplary method may include detecting, at afirst point in time, a difference between a power supply voltage on apower bus in the surgical system and a reference voltage, connecting thepower bus to an alternate power supply contained within a housing of thesurgical system, and detecting, at a second point in time that issubsequent to the first point in time, that the power supply voltage isgreater than the reference voltage. The exemplary method may furtherinclude disconnecting the alternate power supply from the power bus ofthe surgical system.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory innature and are intended to provide an understanding of the presentdisclosure without limiting the scope of the present disclosure. In thatregard, additional aspects, features, and advantages of the presentdisclosure will be apparent to one skilled in the art from theaccompanying drawings and the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate implementations of the devices andmethods disclosed herein and together with the description, serve toexplain the principles of the present disclosure.

FIG. 1 illustrates a perspective view of an exemplary surgical system.

FIG. 2 is an illustration of an exemplary block diagram of the surgicalsystem of FIG. 1.

FIG. 3 is a circuit diagram illustrating an exemplary circuit-basedimplementation of a power loss mitigation system.

FIG. 4 is a circuit diagram illustrating another exemplary circuit-basedimplementation of a power loss mitigation system.

FIG. 5 is a flowchart of an exemplary method of mitigating a short-termpower loss in a surgical system, such as the surgical system of FIG. 1.

The accompanying drawings may be better understood by reference to thefollowing detailed description.

DETAILED DESCRIPTION

For the purposes of promoting an understanding of the principles of thepresent disclosure, reference will now be made to the implementationsillustrated in the drawings. Specific language will be used to describethe same. It will nevertheless be understood that no limitation of thescope of the disclosure is intended. Any alterations and furthermodifications to the described devices, instruments, methods, and anyfurther application of the principles of the present disclosure arefully contemplated as would normally occur to one skilled in the art towhich the disclosure relates. In particular, it is fully contemplatedthat the features, components, and/or steps described with respect toone implementation may be combined with the features, components, and/orsteps described with respect to other implementations of the presentdisclosure. For example, although explanatory references are made to“surgical systems,” other medical systems are included within the scopeof the present disclosure. For simplicity, in some instances the samereference numbers are used throughout the drawings to refer to the sameor like parts.

The present disclosure is directed to systems, circuits, and methods forproviding a continuous power supply during short-term power losses. Suchpower losses include decreases in power outside of normal operatingrequirements, as well as complete power outages in which no electricalpower is supplied. The short-term power losses may be power lossesranging from a few milliseconds to 300, 500, or 1000 milliseconds (ms)or longer, for example. During a surgical procedure, includingdiagnostic and interventional procedures, such power losses mayadversely affect the effectiveness and overall results of the procedure.For example, if a user, such as a surgeon or other medical professional,is performing a surgery on the eye of a patient using a vitrectomycutter, a loss in power may change the performance of the vitrectomycutter. The user may respond to the loss in power by increasing apressure or by otherwise attempting to compensate. As another example,an irrigation probe may be used to maintain visibility during a surgicalprocedure and/or to maintain a desired pressure within a cavity, such asthe posterior segment of the eye. The flow rate of an irrigation probemay be altered, which may cause an unwanted deviation from a safeintraocular pressure. When the power loss ends, the performance of thevitrectomy cutter or the irrigation probe may change again. Therestored, normal performance may cause additional material to be removedthat was not intended to be removed or may cause a sudden increase inintraocular pressure. The loss in power may also result in a computerreset as well, which can alter parameters and stop performance of somesubsystems.

The present disclosure is more specifically directed to a system thatmonitors a voltage supplied by a main power supply to a power busincluded in a system. When the voltage on the power bus drops below athreshold value, the power bus is connected to an alternate power supplythat helps maintain the desired operating voltage. The desired voltagemay be any voltage within a suitable operational range of the system orof a specific component or subsystem. When the main power supply isrestored, the power bus is disconnected from the alternate power supply.The present disclosure includes circuits that provide for suchmonitoring and selective connecting and disconnecting in order tomitigate short-term power losses.

FIG. 1 illustrates an exemplary implementation of an ophthalmic surgicalsystem, generally designated surgical system 100. While the presentdisclosure applies to many different types of surgical systems otherthan the exemplary ophthalmic surgical system 100 and to other medicalsystems, the surgical system 100 is described herein to provideappropriate context for the power loss mitigation systems, circuits, andmethods described herein. As illustrated, the surgical system 100includes a base housing or console 102 and an associated display screen104 showing data relating to system operation and performance during anophthalmic surgical procedure. In some implementations, the console 102may be mobile. For example, some implementations may include wheels orcasters 106 to facilitate movement as necessary or desirable. In someimplementations, the console 102 may not include wheels. The console 102may contain several subsystems that cooperate to enable a surgeon orother user to perform a variety of surgical procedures, such asophthalmic surgical procedures.

An exemplary surgical instrument, which is illustrated as a probe 110,may be coupled to the console 102 by a conduit 108 and may form a partof the surgical system 100. The probe 110 represents any number ofmedical and/or surgical devices, including, for example, a vitrectomyprobe, an illumination probe, an aspiration probe, an irrigation probe,a phacoemulsification device, a diathermy probe, or other types ofmedical devices. The probe 110 may be a handpiece, in someimplementations. The probe 110 may be coupled to one or more subsystemsincluded in the console 102. For example, the probe 110 may be coupledto a probe subsystem that facilitates control of a pump and/or a vacuumfor use in the removal of vitreous or the irrigation of the posteriorsegment of an eye. The probe subsystem may also provide power to theprobe 110 and control operation of the probe 110. The conduit 108 mayinclude cables, tubes, wires, etc. to provide for the operation of theprobe 110 in various implementations. As noted, in some implementations,the probe 110 may be an irrigation probe. In some implementations of thesurgical system 100, the probe 110 may be coupled to multiple consoles,rather than to a single console 102 as illustrated. Such implementationsmay include other conduits in addition to the conduit 108 that connectthe probe 110 to the consoles. The illustrated probe 110 may be used invarious ophthalmic procedures, such as an anterior segment procedure, aposterior segment procedure, a vitreoretinal procedure, a vitrectomyprocedure, a cataract procedure, and/or other procedures. Surgicalprocedures other than ophthalmic procedures may be performed byimplementations of the system 100 and the probe 110.

FIG. 2 is a block diagram of an implementation of the surgical system100 including the console 102 and further depicting several subsystemscontained therein. The console 102 includes a computer subsystem 103configured to communicate with the display screen 104 (FIG. 1), andincludes a number of subsystems that are used together to performsurgical procedures, including ophthalmic surgical procedures, such asemulsification or vitrectomy surgical procedures, for example. Thecomputer subsystem 103 may include one or more processing devices, suchas a central processing unit or central processor, and an information ordata storage system. The data storage system may include one or moretypes of memory, such as RAM, ROM, flash memory, a disk-based harddrive, and/or a solid-state hard drive. The processing devices andstorage system may communicate over a bus 160, which may also permitcommunication with and between one or more of the subsystems of thesurgical system 100.

Some examples of subsystems in the implementation shown in FIG. 2 mayinclude a footpedal subsystem 120 including, for example, a footpedal122, and a fluidics subsystem 130 including an aspiration vacuum 132 andan irrigation pump 134 that connect to a fluid conduit 136. The fluidconduit 136 or a portion thereof may extend between the console 102 andthe probe 110 through the conduit 108 (FIG. 1). The surgical system 100may further include a probe subsystem 112, including the probe 110, andan imaging and control subsystem 140 that is coupled to a communicationmodule 144. The imaging and control subsystem 140 and the communicationmodule 144 may facilitate control of the probe 110 and/or the subsystemsand other features illustrated in FIG. 2.

The surgical system 100 includes a power supply subsystem 150 thatreceives electrical power from electrical AC mains 154 disposed withinthe surgical environment of the surgical system 100. For example, thepower supply subsystem 150 may be coupled by the power supply connector152 to an outlet or outlets disposed within an operating room in ahospital or surgical center. The power supply subsystem 150 may becoupled to a power bus to distribute power within the console 102 to thecomputer subsystem 103 and to the subsystems 112, 120, 130, 140, and toother subsystems included in other implementations of the surgicalsystem 100. The bus 160 may include one or more power buses and one ormore communication buses to provide power to and communication linesbetween the various components of the surgical system 100. The powersupply subsystem 150 may also condition electrical power received fromthe AC mains 154. For example, the power supply subsystem 150 mayconvert received AC electricity to one or more desired DC voltagesand/or other AC voltages. DC voltages, such as 12 V, 24 V, 48 V, may bedistributed by multiple power buses, in some implementations. The otherAC voltages may differ in amplitude and/or frequency. For example, thepower supply subsystem 150 may convert 50 Hz AC voltage to 60 Hz ACvoltage.

The power supply subsystem 150 may further include a power lossmitigation subsystem 156. The power loss mitigation subsystem 156 maymonitor electricity provided by the power supply subsystem 150 to thevarious components of the surgical system 100. When the power lossmitigation subsystem 156 detects that a voltage has fallen below athreshold value, the power loss mitigation subsystem 156 may activate analternate power supply. In some implementations, the power lossmitigation subsystem 156 may detect that a difference between thevoltage and the threshold value has exceeded a threshold. The power lossmitigation subsystem 156 may monitor for the restoration of the powersupply and disconnect the alternate power supply when the voltage risesback above the threshold value. In this way, the power loss mitigationsubsystem 156 may compensate for power losses, i.e., voltage drops belowa threshold value or a complete loss of power to maintain continuouspower to the surgical system 100. The power losses may be short-termpower losses such as power losses lasting a few hundred milliseconds, asecond, or more. Some implementations of the power loss mitigationsubsystem 156 may maintain power supplies for at least 500 ms, enablingat least some components of the surgical system 100 to operateunaffected by the power loss.

Referring now to FIG. 3, shown therein is a power loss mitigationcircuit 200, which may be an implementation of the power loss mitigationsubsystem 156 of the power supply subsystem 150. The power supplysubsystem 150 may include a power supply 202. The power supply 202 mayreceive AC electricity from the AC mains 154 and convert the ACelectricity to DC to be distributed to the components of the surgicalsystem 100. As an example, the power supply 202 may be a 24 VDC powersupply providing 24 V on a power bus 204. The power bus 204 may connectto any of the subsystems of the surgical system 100, including thoseillustrated in FIG. 2 and/or any of the devices connected to the console102, including the probe 110. The power bus 204 may be, or be acomponent of, the bus 160 of FIG. 2. As illustrated, the power bus 204is coupled to the probe 110 to provide power to components thereof, suchas an oscillating vitreous cutter or to controls and circuits containedon or within an irrigation probe. As another example, the power bus 204may be coupled to the fluidics subsystem 130 including the vacuum 132and the pump 134 (FIG. 2).

FIG. 3 also illustrates details of the power loss mitigation circuit200. The power loss mitigation circuit 200 includes various componentsconfigured so as to detect undesired, excessive drops in power and toengage an alternate power supply for a period of time to prevent adverseconsequences that may result from a complete loss of power or from apower loss that goes beyond normal operating conditions.

To monitor the power provided by the power bus 204, the loss mitigationcircuit 200 may include a reference circuit 208 that provides areference value for comparison with the power supply voltage. When thevoltage on the power bus 204 drops below the threshold value provided bythe reference circuit 208, the circuit 200 may operate to connect to thepower bus 204 to an alternate power supply, as will be described infurther detail. As illustrated in FIG. 3, the reference circuit 208comprises a pair of resistors R₁ and R₂ configured as a voltage divider.In other implementations, the reference circuit 208 may be provided by alow-pass RC filter or a capacitive divider. The reference circuit 208may be configured to provide any desired threshold voltage value as afraction or proportion of a normal operating voltage. The desiredthreshold voltage value may be within a normal operating range. Asillustrated, the values of the resistors R₁ and R₂ determine thethreshold value as compared with the voltage on the power bus 204. Asillustrated, R₁ and R₂ may be selected to provide a threshold value of95% of the normal operating voltage on the power bus 204. For example,when the power supply 202 provides 24 V to the power bus 204, thereference circuit 208 may provide the threshold value or referencevoltage of 22.8 V. To provide the 95% threshold value, R₁ may be a 5kOhm resistor and R₂ may be a 95 kOhm resistor, for example. Otherthreshold values and resistor values may be used in otherimplementations. The threshold value may be equal to or close in valueto a low end of a normal operating voltage range of devices orsubsystems coupled to the power bus 204. In some implementations, thethreshold value may be determined specifically by the voltagerequirements of a device used to directly interact with the patientduring a surgical procedure. For example, the voltage requirements ofthe probe 110 may be used to determine the threshold value withoutregard to the voltage requirements of the footpedal subsystem 120.

The reference circuit 208 provides the reference voltage to a sample andhold capacitor 210, C_(SH), which is also coupled to an input of acomparator circuit or comparator 212. The voltage on the sample and holdcapacitor 210 generally tracks the voltage on the power bus 204, whenchanges in the voltage on the power bus 204 are gradual. When thevoltage on the power bus 204 changes quickly, such as from a suddenpower loss, the voltage on the capacitor 210 may not respondimmediately, such that the voltage on the power bus 204 and the voltageon the capacitor 210 depart from their normal proportional relationship.Some implementations of the sample and hold capacitor 210 may have acapacitance ranging from about 0.5 μF to about 1 μF. Other ranges may beused in other implementations. The comparator 212 may be an operationalamplifier based comparator or another comparator circuit. An additionalinput of the comparator 212 may be coupled to the power bus 204. Thecomparator 212 may receive a voltage from the power bus 204 and thereference voltage from the reference circuit 208 (when the switch 214 isclosed and from the capacitor 210 when the switch 214 is open) and maycompare them to each other in order to provide a self-adjusting controlsignal that causes switches in the power loss mitigation circuit 200 toopen or close, when the reference voltage and voltage on the power bus204 diverge. The switch 214 may be referred to herein as the sample andhold switch or S_(SH).

Under normal conditions, the switch 214 may be closed to facilitatecomparison of the voltage on the power bus 204 with the referencevoltage and allow the capacitor 210 to track the voltage on the powerbus during normal operation. Allowing the capacitor 210 to track thevoltage on the power bus 204 allows the power loss mitigation circuit200 to adjust to normal fluctuations caused by changes in temperature,operational drift, etc. The output of the comparator 212 may be coupledto the switch 214 and to a switch 216, which may be referred to as astandby power switch 216 or SST. The switch 216 may be open under normalpower conditions. When the voltage on the power bus 204 suddenly dropsbelow the reference voltage provided by the reference circuit 208, theoutput of the comparator 212 causes the switch 214 to open and theswitch 216 to close. Opening the switch 214 disconnects the capacitor210 from the power bus 204, preventing the voltage on the capacitor 210from dropping along with the voltage on the power bus 204. Closing theswitch 216 couples the power bus 204 to a capacitor 218. The capacitor218 is also referred to as a standby capacitor 218 or C_(ST). Thecapacitor 218 is pre-charged to the voltage level across the capacitor210. Some implementations of the standby capacitor 218 may have acapacitance ranging from 200 μF to about 500 μF. Other implementationsof the standby capacitor 218 may have a lower or a higher capacitance.When connected to the power bus, the standby capacitor 218 may providepower to the power bus 204 such that the power bus 204 maintains avoltage approximately equal to the desired reference voltage, e.g., 95%of the normal operating voltage on the power bus 204.

After the power loss ends and the voltage on the power bus 204 isreturned to 24 V by the power supply 202 (referred to in this example as“normal conditions”), the signal at the output of the comparator 212opens the standby switch 216 and closes the sample and hold switch 214.In this way, the power loss mitigation circuit 200 responds to therestoration of power. Opening the standby switch 216 disconnects thepower bus 204 from the standby capacitor 218 and closing the sample andhold switch 214 reconnects the reference circuit 208 to the sample andhold capacitor 210 and to the input of the comparator 212, reconnectingthe sample and hold capacitor 210 to the power bus 204.

The sample and hold capacitor 210 may also be coupled to an input of adifferential amplifier 220. The differential amplifier 220 may includean additional input coupled to the standby capacitor 218. The signals(voltages) received at the inputs of the differential amplifier 220 maybe processed by the differential amplifier 220 to generate an outputsignal. The output of the differential amplifier 220 may be coupled to aDC/DC step down converter 222. The differential amplifier 220, which maybe implemented by an operational amplifier in some instances, interactswith the DC/DC step down converter 222 to ensure that the voltage on thestandby capacitor 218 tracks the voltage on the sample and holdcapacitor 210. The differential amplifier 220 provides a feedback signalto the DC/DC step down converter 222. For example, when the referencecircuit 208 provides a reference voltage that is 95% of the normalvoltage on the power bus 204, the sample and hold capacitor is chargedto 22.8 V (when the normal voltage is 24 V). The 22.8 V is provided asan input to the differential amplifier 220. The differential amplifier220 outputs a signal to the DC/DC step down converter 222 to ensure thatthe output of the converter 222 is also 22.8 V, causing the other inputof the converter 222 to match the input from the sample and holdcapacitor 218.

In order to supply power to the DC/DC step down converter 222, a boostconverter 224 is connected between the DC/DC step down converter 222 andthe power bus 204, as a first stage of an alternate power supply. Theboost converter 224 may receive power from the power bus 204 andgenerate a high voltage output which is coupled to an input of the DC/DCstep down converter 222. The boost converter 224 may double the voltagereceived at the input, in some implementations. For example, when thepower bus 204 is at 24 V, the boost converter 224 may charge ahigh-voltage capacitor 226 or C_(SH) to 48 V. In some implementations,the boost converter 224 may increase the received voltage by more than afactor of two. Accordingly, the high-voltage capacitor 226, coupled tothe boost converter 224, may be rated to 60 V or more, such as severalhundred volts, in some implementations. Implementations of the capacitor226 may have a capacitance ranging from 2 μF to about 1000 μF. Thegreater the capacitance of the high-voltage capacitor 226, the greaterthe amount of time during which a power loss can be mitigated. Whenpower is to be provided by the standby capacitor 218, acting as analternate power supply, the standby capacitor 218 may be powered by thehigh-voltage capacitor 226 via the DC/DC step down converter 222.

In this way, the alternate power supply may be implemented as atwo-stage power source, in which the boost converter 224 and thehigh-voltage capacitor 226 provide the first stage and the DC/DC stepdown converter 222 and the standby capacitor 218 provide the secondstage. By having the alternate power supply provided by a two-stagepower source, the first stage may permit a higher voltage than isdesired at the output of the alternate power supply. The energy storedon the high-voltage capacitor 226 is proportional to the square of thevoltage, such that the higher voltage on the first stage provides moreenergy storage. The second stage may provide the energy, stored in thefirst stage, at the desired voltage at the output of the alternate powersupply.

The use of the standby capacitor 218 and the high-voltage capacitor 226to mitigate short-term power losses may provide advantages overbattery-based loss mitigation systems. For example, the capacitors 218and 226 are essentially maintenance free, unlike battery-based powerbackup alternatives. In some implementations, the power loss mitigationcircuit 200 may be configured to provide power to only a subset of thesubsystems and instruments connected to the console 102 of FIG. 1. Insuch implementations, additional alternate power supply systems may beincluded in the console 102. For example, a battery-based backup powersupply may be able to supply power to the computing system 103 during apower loss, while the power loss mitigation circuit 200 may supplycontinuous power to the probe 110. In some implementations, more thanone power loss mitigation circuit 200 may be included in the console102.

Referring now to FIG. 4, shown therein is a power loss mitigationcircuit 300 that is similar in many respects to the power lossmitigation circuit 200 of FIG. 3. The power loss mitigation circuit 300may be included in the power supply subsystem 150 as the power lossmitigation subsystem 156 of FIG. 2. In addition to the featuresdescribed with respect to the power loss mitigation circuit 200, thepower loss mitigation circuit 300 may further include a boost switch 302(labeled as SB). The boost switch 302 may be coupled to the output ofthe comparator 212, like the standby switch 216 and the sample and holdswitch 214. Under normal operating conditions, e.g., in the absence of apower loss or a power loss that is less than a threshold amount, theboost switch 302 may be in a closed position to couple the boostconverter 224 to the power bus 204. This may allow the high-voltagecapacitor 226 to be charged as an alternative power supply in the eventof a power loss. When the voltage on the power bus 204 drops below thethreshold value, the output signal from the comparator 212 may cause thestandby switch 216 to close, the sample and hold switch 214 to open, andthe boost switch 302 to open. Opening the boost switch 302 disconnectsthe boost converter 224 from the power bus 204, which may prevent theboost converter 224 from continuing to draw from the power bus 204.

Referring now to FIG. 5, shown therein is flowchart of an exemplarymethod 500 of a mitigating short-term power loss in a medical system. Asillustrated, the method 500 includes several enumerated steps oroperations. Additional operations may be included before, after, inbetween, or as part of the enumerated operations. The method 500 may beimplemented by a system or a circuit. For example, the method 500 may beimplemented by the power supply subsystem 150 of the surgical system 100(FIG. 2) or by the power loss mitigation circuits 200 or 300 of FIGS. 3and 4, respectively.

At 502, a comparator may detect a difference between a power supplyvoltage on a power bus and a reference voltage. With respect to thepower loss mitigation circuit 200, this may be performed by thecomparator 212, which is configured to receive the power supply voltagefrom the power bus 204 and the reference voltage from the referencecircuit 208, when the sample and hold switch 214 is closed, and from thesample and hold capacitor 210, when the switch 214 is open. Thecomparator may detect that the voltage on the power bus is less than thereference voltage.

At 504, the power bus may be connected to an alternate power supply. Forexample, the comparator 212 may detect that the power supply voltage onthe power bus 204 is below the reference voltage and generate an outputcontrol signal that causes the sample and hold switch 214 to open andthe standby switch 216 to close. When the standby switch 216 closes, thepower bus 204 may be connected to the first and second stages of analternate power supply. The first stage of the alternate power supplymay include the boost converter 224 and the high-voltage capacitor 226,while the second stage of the alternate power supply may include theDC/DC step down converter 222 and the standby capacitor 218. An outputof the differential amplifier 220 may be coupled to the DC/DC step downconverter 222 to control the converter 222 to provide charge to thestandby capacitor 218 from the high-voltage capacitor 226.

At 506, the power supply voltage on the power bus may be detected to beabove the reference voltage. For example, after a period time of, suchas 300 ms or 700 ms, the power loss may be resolved and the power supply202 may resume supplying a desired voltage on the power bus 204. Thepower supply voltage may be detected by the comparator 212 as beinggreater than the voltage across the sample and hold capacitor 210. Thecomparator 212 may generate control signals, which may be digitalcontrol signals or analog control signals, to cause the standby switch216 to open and the sample and hold switch 214 to close, therebydisconnecting the alternate power supply from the power bus 204, at 508.

In some implementations of the method 500, the boost switch 302 of FIG.4 may be disconnected or switched off at 504, after the power supplyvoltage on the power bus 204 is determined to be less than the referencevoltage, e.g. outside the normal operating range. The boost switch 302may be reconnected or switched on as part of 508 after the power supplyvoltage is detected as being above the reference voltage. In someimplementations, the power bus 204 may be connected to the standbycapacitor 218 for less than 2 seconds. In some implementations, thecapacitors 226 and 218 may be able to provide power for at least 500 ms.

In some implementations, the method 500 may include an operation ofmeasuring a duration of a power loss. For example, the computersubsystem 103 may monitor the power loss mitigation subsystem 156 ofFIG. 1 to measure how long the switch 214 is open or how long the switch216 is closed. For example, the power loss mitigation subsystem 156 maybe configured to provide for a continuous power supply on the power bus204 for more than a second. At an intermediate point in time (e.g., at500 ms), the computer subsystem 103 may take certain mitigating actions.For example, the computer subsystem 103 may generate commands to savedata, alert a user, and/or put one or more of the subsystems into safemode, in anticipation of a power loss of a longer duration than can besustained by the power loss mitigation subsystem 156. In this way, evenwhen the power loss exceeds the ability of the power loss mitigationsubsystem 156 to provide power, implementations of the power lossmitigation subsystem 156 may provide time to take actions to mitigatesuch longer power loss.

Implementations of the present disclosure may include surgical systems,circuits, and methods for providing a short-term alternate power supplywhen a main power supply experiences a power loss. The alternate powersupply may include one or more capacitors that may be charged duringnormal operation of the surgical system. The alternate power supply maybe included within the surgical system alongside one or more additionalalternate power supplies. The alternate power supply may be configuredto supply power to a surgical instrument to minimize potential risksthat could be caused to a patient as a result of a power loss. Thealternate power supply may provide a maintenance-free power sourceduring power losses lasting for more than 500 ms or more than onesecond. The alternate power supply may be automatically engaged when thevoltage on a power bus drops below a minimum threshold and automaticallydisengaged when the voltage on the power bus rises above the minimumthreshold again. In this manner, embodiments of the present disclosuremay provide a self-adjusting short-term alternate power supply tominimize potential risks to a patient during a surgical procedure.

Persons of ordinary skill in the art will appreciate that theimplementations encompassed by the present disclosure are not limited tothe particular exemplary implementations described above. In thatregard, although illustrative implementations have been shown anddescribed, a wide range of modification, change, and substitution iscontemplated in the foregoing disclosure. It is understood that suchvariations may be made to the foregoing without departing from the scopeof the present disclosure. Accordingly, it is appropriate that theappended claims be construed broadly and in a manner consistent with thepresent disclosure.

What is claimed is:
 1. A surgical system comprising: a fluidicssubsystem; a surgical instrument subsystem that couples to a surgicalinstrument, wherein the surgical instrument is coupled to the fluidicssubsystem; and a power supply subsystem coupled to the surgicalinstrument subsystem, the power supply subsystem comprising: a mainpower supply connectable to AC mains to generate a voltage; a power busconnected to the main power supply; an alternate power supply; and acircuit that monitors the voltage on the power bus for powering thesurgical instrument subsystem and automatically connects the power busto the alternate power supply when the voltage drops below a referencevoltage due to a power loss from the main power supply.
 2. Theophthalmic surgical system of claim 1, wherein the alternate powersupply comprises at least two capacitors.
 3. The ophthalmic surgicalsystem of claim 2, wherein the alternate power supply comprises atwo-stage alternate power supply.
 4. The ophthalmic surgical system ofclaim 3, wherein a first stage of the two-stage alternate power supplyis coupled to the power bus and a high-voltage capacitor and wherein asecond stage of the two-stage alternate power supply is coupled to astandby capacitor that is coupled to the power bus by a switch.
 5. Theophthalmic surgical system of claim 1, wherein the reference voltage isprovided by a reference circuit having an output connected to thecircuit by a switch.
 6. The ophthalmic surgical system of claim 3,wherein the first stage of the two-stage alternate power supplycomprises a boost converter and a high-voltage capacitor configured tostore electrical energy.
 7. The ophthalmic surgical system of claim 6,wherein the boost converter is coupled to the power bus by a switch thatis opened when the power bus is connected to the alternate power supply.8. The ophthalmic surgical system of claim 1, wherein the power supplysubsystem further comprises a differential amplifier that receives thereference voltage and an output voltage of the alternate power supply asinputs and generates a control signal for a step down converter includedin the power supply subsystem.
 9. The ophthalmic surgical system ofclaim 1, wherein the at least one surgical instrument subsystemcomprises an irrigation probe, and wherein the irrigation probe iscoupled to a console by a conduit, the console containing the alternatepower supply.
 10. A surgical system comprising: a surgical instrumentsubsystem, the surgical instrument subsystem comprising a connection toa surgical instrument; and a power supply subsystem coupled to thesurgical instrument subsystem that comprises: a main power supplyconnectable to AC mains to generate a voltage; a power bus connected tothe main power supply; an alternate power supply; and a circuit thatmonitors the voltage on the power bus and automatically connects thepower bus to the alternate power supply when the voltage drops below areference voltage due to a power loss from the main power supply. 11.The surgical system of claim 10, wherein the alternate power supply iscoupled to the power bus at an input and includes a high-voltagecapacitor coupled by a step down converter to a standby capacitor at anoutput.
 12. The surgical system of claim 11, wherein the alternate powersupply comprises a two-stage alternate power supply, wherein a firststage of the two-stage alternate power supply is coupled to the powerbus at an input and to a high-voltage capacitor at an output and whereina second stage of the two-stage alternate power supply is coupled to thehigh-voltage capacitor at an input and to a standby capacitor at anoutput, and wherein the second stage of the two-stage alternate powersupply is coupled to the power bus by a switch.
 13. The surgical systemof claim 10, wherein the circuit is a comparator having an outputcoupled to the switch.
 14. The surgical system of claim 10, wherein thecircuit is a comparator having an output coupled to a switch at an inputto a first stage of the alternate power supply and a switch at an outputof a second stage of the alternate power supply.
 15. The surgical systemof claim 14, wherein the reference voltage is provided by a referencecircuit having an output connected to the circuit by a switch that isautomatically opened when the voltage drops below reference voltage dueto the power loss from the main power supply.
 16. The surgical system ofclaim 10, wherein the power supply subsystem further comprises adifferential amplifier that receives the reference voltage and an outputvoltage of the alternate power supply as inputs and generates a controlsignal for a step down converter included in the alternate power supply.17. The surgical system of claim 10, wherein the surgical instrumentsubsystem comprises an irrigation probe, and wherein the irrigationprobe is coupled to a console by a conduit, the console containing thealternate power supply.
 18. A method of mitigating a short-term powerloss in a surgical system, the method comprising: detecting, at a firstpoint in time, a difference between a power supply voltage on a powerbus in the surgical system and a reference voltage; connecting the powerbus to an alternate power supply contained within a housing of thesurgical system; detecting, at a second point in time that is subsequentto the first point in time, that the power supply voltage is greaterthan the reference voltage; and disconnecting the alternate power supplyfrom the power bus of the surgical system.
 19. The method of claim 18,wherein detecting the difference between the power supply voltage on thepower bus in the surgical system and the reference voltage comprisesutilizing a comparator that is connected to the power bus at a firstinput into a reference circuit supplying the reference voltage at asecond input.
 20. The method of claim 18, wherein disconnecting thealternate power supply from the power bus of the surgical systemcomprises opening a first switch between an output of the alternatepower supply and the power bus and closing a second switch between areference circuit and a comparator.